Is There Any Relationship between Vitamin D Deficiency and Gross Motor Development in 12-Month-Old Children?

Objective
We aimed to assess the possible relationship between vitamin D deficiency and gross motor developmental milestones in Iranian children in Tehran City, Iran.


Materials & Methods
In this cross-sectional study, 186 healthy children of one-yr-old age referring to a children hospital in Tehran, Iran from May 2015 to April 2016, were enrolled. The gross motor developmental milestone of children and their serum vitamin D concentration were evaluated.


Results
Overall, 186 children, 92 males (49.5%) were studied. Twenty-four patients (12.9%) just were able to sit without support, and 40 patients (21.5%) to stand alone and to sit without support. Besides, 122 patients (65.6%) were able to walk with assistant or alone and to sit without support and stand alone. Vitamin D was sufficient in 148 children (79.6%), insufficient in 32 (17.2%) and deficient in 6 (3.2%). Sufficient vitamin D was significantly correlated with walking ability (P<0.001, OR=3.9, 95%CI=1.9-8.4).


Conclusion
Considering the significant correlation between vitamin D deficiency and gross motor developmental milestones in this population of children, children referring to gross motor developmental delay need to be thoroughly evaluated for vitamin D deficiency.


Introduction
Vitamin D is important for skeletal growth and cellular function due to its role in calcium homeostasis through regulating calcium absorption in bowel (1). Additional health benefits of vitamin D have been anticipated in children such as prevention of type 1 diabetes mellitus, asthma, cardiovascular disease, influenza and respiratory infections (2)(3)(4)(5). In children, vitamin D has a role in motor development (6,7). Vitamin D deficiency is a common condition in children. Particularly those who have chronic disease, malnourished, have geographically limited sun exposure, as well as those with darker skin, and chronically using special medications (8,9).
In case of vitamin D deficiency, bowel absorption of calcium and phosphorus is reduced and the parathyroid gland responds to low serum calcium levels by producing parathyroid hormone (PTH) to increase the serum calcium to an acceptable level.
PTH increases calcium reabsorption in the kidneys and excretion of phosphorus, thus reducing the adverse complication of elevated calcium phosphate products (10,12). Over weeks to months stunting, rickets and osteomalacia might appear (13,14). Children`s vitamin D insufficiency also may prevent children achieving their peak bone mass and genetically programmed height (13). The enhanced rate of bone growth in children implies how inadequate level of vitamin D in this period of life can damage this process (8).
Vitamin D status is important for motor development in children (6,7); however, more researches are needed to evaluate the association of vitamin D status in pediatric patients with developmental status (15).
The prevalence of vitamin D deficiency is reported considerably higher in Middle-Eastern countries.

The incidence of Vitamin D deficiency among
Iranian children is 85.6% (16,17).
Even though there is high prevalence of Vitamin D deficiency among Iranian children; based on our knowledge the relation between Vitamin D levels and motor development in children has not ever been evaluated in Iran. Therefore, in this study, we aimed to assess the possible relationship between vitamin D deficiency and gross motor developmental milestones in one-year-old Iranian children in Tehran City.

Materials & Methods
In this cross-sectional study, 186 twelve-month-old children referred to a university hospital in Tehran, Iran from May 2015 to April 2016, were enrolled.

The study was approved by the Research Ethics
Committee of Tehran University of Medical Sciences, Tehran, Iran. Informed parental consent was obtained prior to sampling.
The inclusion criteria included term delivery, twelve-month-old, without any history of asphyxia, neuromuscular disease, metabolic diseases, Down syndrome and any previous major disease.
The sampling was convenience. Demographic data such as gender were recorded. Gross motor development was assessed by a pediatrician.
Three distinct gross motor milestones were selected as follows: sitting without support; standing alone and walking with assistant or alone.
These three milestones were selected considering that most of twelve-month-old children have the ability to perform them based on various existing developmental scale (18,19). Moreover, they are universal and simple to test and evaluate.
Therefore, administration and interpretation of the child's performance could be cleared (18,19).
Twenty-four patients (12.9%) just were able to sit without support, 40 patients (21.5%) were able to stand alone, and to sit without support. Besides, 122 patients (65.6%) were able to walk with assistant or alone, in addition to sit without support and stand alone.
There was no significant relationship between gender and gross motor development (P=0.58).
There was a significant relation between Vitamin D status and motor development in our participants (P<0.001). Of six children with Vitamin D deficiency, one case (16.7%) could walk and 1 case (16.7%) could stand alone. Four cases (66.7%) were able to sit without support (Table 1).

Discussion
One common clinical symptom in Vitamin D-associated rickets is motor developmental delay in children (6,7).
In the present study, 12.9% of children were able to sit without support, 21.5% were able to stand alone and 65.6% were able to walk. In case of A retrospective study on children suffering from hypocalcemia or rickets because of vitamin D after 3 wk of treatment. Seventeen patients were able to walk 3 months after treatment (6).
Moreover, walking delay was reported as one of severe Vitamin D deficiency complications (24).
In England 17 children hospitalized because of secondary hypocalcemic convulsion due to Vitamin D deficiency were studied and showed delay in motor development especially walking as the most common complication (25). Vitamin D deficiency in children can be the cause of gross motor delay among them and both of them were consistent.
In conclusion, Vitamin D deficiency in children is associated with motor development delay. Children referring to physicians with motor developmental delay need to be checked for Vitamin D, in order to administer appropriate doses of Vitamin D and prevent further continuation of motor developmental delay.